GB2499670A

GB2499670A - Common feedback for coordinated multi-point operations

Info

Publication number: GB2499670A
Application number: GB201203361A
Authority: GB
Inventors: Mihai Horatiu Enescu; Tommi Tapani Koivisto; Helka-Liina Maattanen; Karol Schober
Original assignee: Renesas Mobile Corp
Current assignee: Renesas Electronics Corp
Priority date: 2012-02-27
Filing date: 2012-02-27
Publication date: 2013-08-28
Also published as: GB201203361D0

Abstract

A common feedback framework for coordinated multi-point (CoMP) operations of various coordinated multi-point schemes (such as joint transmission (JT), dynamic point selection (DPS) or coordinated scheduling / beamforming (CS/CB)), comprising generation of channel state information (CSI) feedback for coordinated multi-point operations, said generating comprising jointly encoding rank indicator information as a per-point feedback component with respect to a single transmission point and at least one of inter-point feedback components with respect to multiple transmission points into a joint channel state information feedback component, and signalling of the generated channel state information feedback from a coordinated multi-point user entity to a coordinated multi-point controller entity; and control of coordinated multi-point operations on the basis of the received channel state information feedback at the coordinated multi-point controller entity.

Description

1

Communications Methods, Apparatus and Computer Program Products Technical Field

Some embodiments of the present invention relate to measures including 5 communications methods and apparatus and computer program products for providing a common feedback framework for coordinated multi-point operations. More specifically, some embodiments of the present invention relate to measures including communications methods, apparatuses and computer program products for realizing a common feedback framework for coordinated multi-point operations of 10 various coordinated multi-point schemes and/or scenarios.

Background

In modern (wireless and/or cellular) communication systems, such as e.g. LTE and LTE-A and its successors, multiple-input multiple-output (MIMO) systems, 15 including single-user (SU-) and multi-user (MU-) MIMO systems, are gaining increasing attention and importance. Such MIMO systems typically suffer from a liability to network performance limitations in view of (e.g. inter-cell) interference, especially at cell edges.

Also, coordinated multi-point (CoMP) transmission/reception operations are 20 adopted as a technique for improving coverage of high data rates, cell-edge throughput/performance, and system throughput/performance. In downlink CoMP operations, multiple points (which in practice may typically be base stations, access nodes or the like) co-operate in scheduling and transmission of downlink communications in order to strengthen a desired signal and mitigate inter-cell 25 interference. In this regard, a point is regarded as a set of geographically co-located transmit antennas at one site, and the sectors of the same site correspond to different points. A cell may be formed by one or multiple points, meaning that one cell can comprise transmit antennas co-located at a single geographical location and/or distributed over multiple geographical locations.

30 In terms of CoMP, intra- and inter-cell downlink CoMP operations in homogeneous and heterogeneous network deployments are specifically considered.

In the context of CoMP operations, various CoMP schemes (also referred to as CoMP categories) are considered. Such CoMP schemes specifically include joint transmission (JT), dynamic point selection (DPS), and coordinated

2

scheduling/beamforming (CS/CB). In joint transmission (JT) CoMP, two or more points transmit simultaneously to a CoMP user. Dynamic point selection (DPS) refers to a CoMP scheme where the transmission point is switched according to changes in channel and interference conditions. In coordinated beamforming/scheduling (CB/CS) 5 CoMP, the scheduling decisions of neighbor points are coordinated in order to reduce interference. In principle, all of these CoMP schemes may include dynamic point blanking/muting which means that one or more transmission points are blanked/muted (i.e. turned off) to decrease interference.

In the context of CoMP operations, various CoMP scenarios are considered as 10 well. Such CoMP scenarios specifically include an intra-site scenario (in a homogeneous network) where multiple co-located sectors of the same base station site are cooperating (referred to as scenario 1), an inter-site scenario (in a homogeneous network) with high power remote radio heads (RRH) where multiple non-co-located points having the same transmit power are cooperating (referred to as scenario 2), a 15 heterogeneous network scenario with low power RRHs within the coverage of a high power macro cell, each operating in/as its own cell (referred to as scenario 3), and a heterogeneous network scenario with low power RRHs within the coverage of a high power macro cell, each operating in/as the same cell (referred to as scenario 4).

Generally, CoMP operations rely on feedback. Namely, a CoMP transmission 20 point typically relies on channel state information (CSI) feedback from a CoMP user. In downlink CoMP operations, such CSI feedback is to be provided in the uplink direction from a terminal or user equipment serving as the CoMP user to a base station, access node, or the like serving as the CoMP transmission point.

For the different CoMP schemes mentioned above, different types and/or 25 contents of CSI feedback are effective or required for the CoMP transmission point so as to perform the respective CoMP scheme in an efficient and appropriate manner. For the different CoMP scenarios mentioned above, different types and/or references of CSI feedback, including differences in feedback signaling path, transmission properties, and the like, are effective or required so as to provide the CSI feedback to 30 the CoMP transmission point in an efficient and appropriate manner.

In view thereof, when CoMP operations are implemented in a variety of CoMP schemes and/or CoMP scenarios, there is a problem in providing appropriate CSI feedback in an appropriate manner for supporting any conceivable CoMP operation.

3

Accordingly, there is a desire or even need to realize a common feedback framework for coordinated multi-point operations of various coordinated multi-point schemes and/or scenarios.

5 Summary

Various exemplary embodiments of the present invention aim at addressing at least part of the above issues and/or problems and drawbacks.

Various aspects of exemplary embodiments of the present invention are set out in the appended claims.

10 According to an exemplary aspect of the present invention, there is provided a communications method comprising generating channel state information feedback for coordinated multi-point operations, said generating comprising jointly encoding rank indicator information as a per-point feedback component with respect to a single transmission point and at least one of inter-point feedback components with respect to 15 multiple transmission points into a joint channel state information feedback component, and signaling the generated channel state information feedback to a coordinated multi-point controller entity.

According to an exemplary aspect of the present invention, there is provided a communications method comprising receiving channel state information feedback for 20 coordinated multi-point operations, said channel state information feedback comprising a joint channel state information feedback component in which rank indicator information as a per-point feedback component with respect to a single transmission point and at least one of inter-point feedback components with respect to multiple transmission points are jointly encoded, and controlling coordinated multi-25 point operations on the basis of the received channel state information feedback.

According to an exemplary aspect of the present invention, there is provided a communications apparatus (which may e.g. be arranged/configured for use on a terminal side of a cellular system), comprising a processing system arranged to cause the apparatus to perform: generating channel state information feedback for 30 coordinated multi-point operations, said generating comprising jointly encoding rank indicator information as a per-point feedback component with respect to a single transmission point and at least one of inter-point feedback components with respect to multiple transmission points into a joint channel state information feedback component, and signaling the generated channel state information feedback to a

4

coordinated multi-point controller entity. The processing system may comprise at least one processor, at least one memory including computer program code, and at least one interface configured for communication with at least another apparatus, the at least one processor.

5 According to an exemplary aspect of the present invention, there is provided a communications apparatus (which may e.g. be arranged/configured for use on a network side of a cellular system), comprising a processing system arranged to cause the apparatus to perform: receiving channel state information feedback for coordinated multi-point operations, said channel state information feedback 10 comprising a joint channel state information feedback component in which rank indicator information as a per-point feedback component with respect to a single transmission point and at least one of inter-point feedback components with respect to multiple transmission points are jointly encoded, and controlling coordinated multipoint operations on the basis of the received channel state information feedback. The 15 processing system may comprise at least one processor, at least one memory including computer program code, and at least one interface configured for communication with at least another apparatus, the at least one processor.

According to an exemplary aspect of the present invention, there is provided a computer program product comprising computer-executable computer program code 20 which, when the program is run on a computer (e.g. a computer of an apparatus according to any one of the aforementioned apparatus-related exemplary aspects of the present invention), is configured to cause the computer to carry out the method according to any one of the aforementioned method-related exemplary aspects of the present invention.

25 Such computer program product may comprise or be embodied as a (tangible)

computer-readable (storage) medium or the like on which the computer-executable computer program code is stored, and/or the program may be directly loadable into an internal memory of the computer or a processor thereof.

Advantageous further developments or modifications of the aforementioned 30 exemplary aspects of the present invention are set out in the following.

By virtue of any one of the aforementioned exemplary aspects of the present invention, a common feedback signaling design for various coordinated multi-point schemes and/or scenarios is achievable, which is effective in terms of allowing

5

seamless coordinated multi-point operations and providing fallback support to single-point operations.

By way of exemplary embodiments of the present invention, there is provided a common feedback framework for coordinated multi-point operations. More 5 specifically, by way of exemplary embodiments of the present invention, there are provided measures and mechanisms for realizing a common feedback framework for coordinated multi-point operations of various coordinated multi-point schemes and/or scenarios (in/for cellular communication systems).

Thus, enhancements and/or improvements are achieved by methods, 10 apparatuses and computer program products capable of realizing a common feedback framework for coordinated multi-point operations, namely coordinated multi-point operations of various coordinated multi-point schemes and/or scenarios.

Brief Description of Drawings 15 For a more complete understanding of exemplary embodiments of the present invention, reference is now made to the following description taken in connection with the accompanying drawings in which:

Figure 1 shows a diagram of an example of a procedure in a CoMP system according to exemplary embodiments of the present invention,

20 Figure 2 shows a flowchart of an example of a procedure at a CoMP user entity according to exemplary embodiments of the present invention,

Figure 3 shows a diagram of an example of another procedure in a CoMP system according to exemplary embodiments of the present invention,

Figure 4 shows a diagram of an example of still another procedure in a CoMP 25 system according to exemplary embodiments of the present invention,

Figure 5 shows a table illustrating a mapping of CSI feedback components in a predetermined signaling format according to conventional specifications and exemplary embodiments of the present invention, and

Figure 6 shows a schematic block diagram illustrating exemplary apparatuses 30 according to exemplary embodiments of the present invention.

Detailed Description

Exemplary aspects of the present invention will be described herein below. More specifically, exemplary aspects of the present are described hereinafter with

6

reference to particular non-limiting examples and to what are presently considered to be conceivable embodiments of the present invention. A person skilled in the art will appreciate that the invention is by no means limited to these examples, and may be more broadly applied.

5 It is to be noted that the following description of the present invention and its embodiments mainly refers to specifications being used as non-limiting examples for certain exemplary network configurations and deployments. Namely, the present invention and its embodiments are mainly described in relation to 3GPP specifications being used as non-limiting examples for certain exemplary network configurations 10 and deployments. In particular, a LTE/LTE-Advanced communication system is used as a non-limiting example for the applicability of thus described exemplary embodiments. As such, the description of exemplary embodiments given herein specifically refers to terminology which is directly related thereto. Such terminology is only used in the context of the presented non-limiting examples, and does naturally 15 not limit the invention in any way. Rather, any other network configuration or system deployment, etc. may also be utilized as long as compliant with the features described herein.

In particular, the present invention and its embodiments may be applicable in any (cellular) communication system and/or network deployment in which 20 coordinated multi-point (CoMP) transmission/reception operations, particularly coordinated multi-point (CoMP) operations of various coordinated multi-point schemes and/or scenarios, are operable.

Hereinafter, various embodiments and implementations of the present invention and its aspects or embodiments are described using several alternatives. It is 25 generally noted that, according to certain needs and constraints, all of the described alternatives may be provided alone or in any conceivable combination (also including combinations of individual features of the various alternatives).

According to exemplary embodiments of the present invention, in general terms, there are provided mechanisms, measures and means for common feedback 30 framework for coordinated multi-point operations of various coordinated multi-point schemes and/or scenarios.

Generally, the present invention and its exemplary embodiments are applicable to any CoMP schemes and/or scenarios, including those mentioned herein as well as

7

any other conceivable CoMP schemes and/or scenarios available at present and/or in the future.

In the following, exemplary embodiments of the present invention are described with reference to methods, procedures and functions, as well as with 5 reference to structural arrangements and configurations.

Generally, any procedures according to exemplary embodiments of the present invention are operable at a CoMP user entity and/or at a CoMP controller entity and/or between the same. As described herein below, a CoMP user entity may be implemented at/in/by any terminal side entity of a cellular communication system, 10 such as a UE or the like, and a CoMP controller entity may be implemented at/in/by any network side entity of a cellular communication system (capable of controlling CoMP transmission/reception and/or operation, e.g. (CoMP) transmission points), such as an eNB or the like.

It is noted that the CoMP controller entity may or may not be co-located with a 15 CoMP transmission (TX) point. That is, while the CoMP user entity is served by, i.e. communicates with, one or more TX points (e.g. CoMP TX points), the CoMP controller entity may be implemented at/in/by a different site or apparatus than the one or more TX points (e.g. CoMP TX points).

Any procedures according to exemplary embodiments of the present invention 20 or, stated in other words, the underlying CoMP system comprising a CoMP user entity and a CoMP controller entity, are operable in any conceivable CoMP scenario. For example, referring to the above-mentioned CoMP scenarios, in CoMP scenario 1 a CoMP controller entity may be operable at/in/by a base station (in a homogeneous network), i.e. a sector of (the transmit antennas) thereof cooperating with another 25 sector of (the transmit antennas) thereof, in CoMP scenario 2 a CoMP controller entity may be operable at/in/by a high power remote radio head or base station (in a homogeneous network), i.e. an access point at a specific base station site cooperating with another access point at a different base station site, in CoMP scenario 3 a CoMP controller entity may be operable at/in/by a low power remote radio head or base 30 station within the coverage of a high power macro cell or base station (in a heterogeneous network), i.e. an access point at a specific base station site cooperating with another access point at a different base station site, which operate in /as different cells, and in CoMP scenario 4 a CoMP controller entity may be operable at/in/by a low power remote radio head or base station within the coverage of a high power

8

macro cell or base station (in a heterogeneous network), i.e. an access point at a specific base station site cooperating with another access point at a different base station site, which operate in /as the same cell.

Figure 1 shows a diagram of an example of a procedure in a CoMP system 5 according to exemplary embodiments of the present invention.

As shown in Figure 1, a corresponding procedure according to exemplary embodiments of the present invention, at the CoMP user entity, comprises an operation of generating CSI feedback for CoMP operations (being applicable e.g. at a CoMP controller entity), wherein said generating comprises jointly encoding rank 10 indicator information (RI) as a per-point feedback component with respect to a single (e.g. serving CoMP) TX point and at least one of inter-point feedback components with respect to multiple (e.g. CoMP) TX points into a joint CSI feedback component, and an operation of signaling the generated CSI feedback to a CoMP controller entity. Further, a corresponding procedure according to exemplary embodiments of the 15 present invention, at the CoMP controller entity, comprises an operation of receiving this CSI feedback comprising the joint CoMP feedback component from the CoMP user entity, and an operation of controlling CoMP operations on the basis of the received CSI feedback with the joint CoMP feedback component.

Generally, while reference is mostly made to CoMP TX points herein by way 20 of example and clarity of description only, such denomination is not to be construed as limiting regarding the applicability of transmission points (such as antennas). That is, any conceivable transmission point (such as antenna) is applicable as a TX point according to exemplary embodiments of the present invention, and it does not have to be specifically configured or characterized as a CoMP(-capable) transmission point 25 (or antenna).

According to exemplary embodiments of the present invention, the CSI feedback may be signaled to the CoMP controller entity via the single TX point, via one or more of the multiple TX points (which may e.g. include the single TX point), or via none of the single/multiple TX points.

30 According to exemplary embodiments of the present invention, the received

CSI feedback is taken into consideration in the controlling operation. Yet, it is noted that the CSI feedback constitutes sort of suggestion or recommendation for the CoMP controller entity, so the CoMP controller entity does not have to obey such CSI feedback. Accordingly, the controlling operation may comprise performing one or

9

more of the CoMP operations, preferably based on the CSI feedback, or refraining from any CoMP operations but e.g. perform a SU-MIMO operation or the like for fallback purposes. Accordingly, a scheduling operation or the like for the CoMP user entity may be decided at the CoMP controller entity based on the CSI feedback to be 5 applicable in a single cell, to be applicable in a CoMP manner, to be not at all applicable, or the like.

In terms of the receiving and/or controlling operation, the CoMP controller entity may decode the CSI feedback, in particular the joint CSI feedback component. Upon decoding, the thus decoded rank indicator information (RI) may be applied as a 10 per-point feedback component in terms of the CoMP operation/s and/or the thus decoded at least one inter-point feedback component may be applied as an inter-point feedback component in terms of the CoMP operation/s.

According to exemplary embodiments of the present invention, the inter-point feedback components may at least comprise CoMP rank indicator information 15 (RICoMP), CoMP scheme selection information (CSS), and layer order indicator information (ROI) of transmission layers or streams between a number of CoMP TX points corresponding to the CoMP rank indicator information.

As used herein, feedback components applicable for exemplary embodiments of the present invention may be the following.

20 On the one hand, one or more of the following per-point feedback components

(also referred to as per-CSI-RS resource feedback components when being based on channel measurement on the basis of CSI RS configurations, as outlined below) are applicable:

- rank indicator information (RI) indicating a (recommended) number of 25 spatially multiplexed transmission layers or streams for a CoMP TX point;

- precoding matrix indicator information (PMI) indicating a (recommended) precoder index, e.g. in a predetermined codebook, wherein eachprecoder index indicates antenna weights to be applied at the transmit antennas for optimum performance; and

30 - channel quality indicator information (CQI) indicating the modulation and/or coding scheme to be applied, hence enabling for link adaptation at the network side.

10

On the other hand, one or more of the following inter-point feedback components (also referred to as inter-CSI-RS resource feedback components when being based on channel measurement on the basis of CSI RS configurations, as outlined below) are applicable:

5 - CoMP rank indicator information (RICoMP), i.e. a rank indicator for CoMP

mode, indicating a (recommended) number of spatially multiplexed transmission layers or streams over multiple CoMP TX points; the rjCoMP may be higher than per-point RI (i.e. a SU-MIMO rank indicator) if (main) interference is removed by at least one CoMP scheme/operation; 10 - CoMP scheme selection information (CSS) indicating a particular CoMP

scheme/operation and corresponding assumptions on what each CoMP point is transmitting (i.e. if they transmit a useful signal, interference or are not transmitting), in other words the reference transmission scheme that the CoMP user entity would assume for CQI calculation; the CSS may form a codeword 15 while the multiple CoMP schemes and CQI assumptions may form a codebook containing all these options; in particular, the CSS may assume common rank among coordinating CoMP points; in conjunction with the ROI, CSS and ROI can allow flexible rank assumption per point; and layer order indicator information (ROI), which is specifically a ROI of 20 transmission layers or streams between a number of CoMP TX points corresponding to the CoMP rank indicator information, indicating a layer ordering; namely, the ROI corresponds to a composite rank which indicates a specific order of the transmission layers or streams transmitted from different CoMP points; the ROI is particularly effective when different CoMP TX 25 points have different per-point transmission rank (for example rank 1 from one point and rank 2 from another point); the ROI may be a codeword selected from a codebook which describes possible layer order combinations from the CoMP transmission points.

Hereinafter, CSS is represented as plain text information. Yet, it is noted that 30 any such plain text representation is to correspond an appropriate codeword representing a corresponding CoMP scheme selection information.

Hereinafter, the following notation is used for ROI codewords. Namely, example of different per-point rank entries in a ROI codebook may for example be as follows (when assuming CoMP with two CoMP TX points):

11

-^•11 "^12

■^•11 "^12

" 1„

"^11 "^12

l2i 122

wherein In and In represent first and second layers/streams transmitted from a first point, while hi and I22 represent first and second layers/streams transmitted from a second point. The top row represents the stronger/strongest point. Accordingly, column-wise, if two layers exist, this means that they can be sent in coherent or noncoherent manner from the two points, while, if no layer exists from a specific point, this means that no transmission is done on that layer from that point (i.e. that point is muted).

"hi ~

For example, the codebook entry

^22 hi means that the first stronger point

(top horizontal row) is in rank 1 (perhaps due to line of sight conditions), while the weaker point (bottom row) is in rank 2. The layer of the first point, In, is paired with the second (weakest) layer of the second point, I22, while the strongest layer of the second point, l2i, is transmitted alone.

Further codebook entries of the ROI may indicate layer flipping, e.g.

, or rank extension, e.g.

X

A 2

i

'hi

A 2

X

^22 _

7

J 22

hi _

'III

1

i

1

J 21

1

7

1

<N

1

It is to be noted that that ROI may also implicitly include the riCoMP and/or fallback rank RI.

According to exemplary embodiments of the present invention, the joint encoding may comprise one of various optional combinations of the RI and the aforementioned inter-point feedback components. Specifically, there are the following options according to exemplary embodiments of the present invention:

- the RI and the rjCoMP may be jointly encoded into the joint CSI feedback component,

- the RI and the CSS may be jointly encoded into the joint CSI feedback component,

- the RI and the rjCoMP and the CSS may be jointly encoded into the joint CSI feedback component, and

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- the RI and the ROI may be jointly encoded into the joint CSI feedback component,

- the RI and the CSS and the ROI may be jointly encoded into the joint CSI feedback component,

5 - the RI and the rjCoMP and the ROI may be jointly encoded into the joint CSI

feedback component,

- the RI and the rjCoMP and the CSS and the ROI may be jointly encoded into the joint CSI feedback component.

In view of the aforementioned optional combinations for joint encoding, the 10 following is noted.

In case of joint encoding of RI only with RICoMP, layer ordering (i.e. ROI) and CSS for CoMP are pre-defined (either specified or configured to the CoMP user entity). In case of joint encoding of RI with RICoMI' and CSS, layer ordering (i.e. ROI) for CoMP is pre-defined (either specified or configured to the CoMP user entity). In 15 case of joint encoding of RI with the layer ordering (i.e. ROI), ROI implicitly includes

RjCoMP

While the aforementioned optional combinations for joint encoding are explicitly mentioned herein, it is to be noted that any other optional combinations for joint encoding not explicitly mentioned herein are equally applicable according to 20 exemplary embodiments of the present invention. Namely, any conceivable sub-/set of any conceivable examples of inter-point feedback components may be jointly encoded with the rank indicator information (RI). The actual applicability/preference of certain combinations for implementation may be a trade-off between overhead and performance, or the like.

25 It is noted that the sequence of mention of the individual feedback components in the present description is not relevant in terms of the joint encoding according to exemplary embodiments of the present invention. For example, a joint encoding being referred to as "RI + rjcomp" is equivalent to a joint encoding being referred to as "RIcomp + RI", and so on.

30 The usage of the RI as a per-point feedback component with respect to a single

(e.g. the serving) CoMP TX point according to exemplary embodiments of the present invention provides for fallback support to single-point operations, i.e. conventional single-point schemes/operations. Accordingly, the CoMP controller entity receiving the thus configured CSI feedback according to exemplary embodiments of the present

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invention is enabled to fall back to such single-point operations, as needed or appropriate, e.g. in view of the contents of the CSI feedback information or other environmental conditions or the like. Accordingly, the CoMP controller entity may act as a fallback CoMP controller entity or TX point.

5 As evident from the above, exemplary embodiments of the present invention propose to jointly encode the existing RI with (LTE/LTE-A) inter-point (inter-CSI-RS resource) feedback information, i.e. CoMP feedback information, wherein the inter-point (inter-CSI-RS resource) feedback information may comprise CoMP transmission hypothesis in terms of transmitting/interfering/muting points, 10 transmission rank as well as layer ordering between points. In other words, the CoMP feedback information may comprise RICoMP, CSS (optionally including point selection), ROI, and any combinations thereof.

According to exemplary embodiments of the present invention, for realizing any one of the aforementioned options for the joint encoding, a codebook (i.e. a set of 15 codewords) for the CSI feedback may be prepared (and an appropriate codeword from such codebook may be selected at the CoMP user entity) in accordance with the at least one inter-point feedback component being jointly encoded with the rank indicator information into the joint CSI feedback component, i.e. in accordance with the applied option of joint encoding.

20 In the following, different exemplary codebooks according to exemplary embodiments of the present invention are described. It is to be noted that the thus exemplified codebooks are merely explained by way of example for explanatory and illustrative purposes, but do not limit the present invention or its embodiments by no means.

25 It is to be noted that all of the codebooks exemplified below may be based on,

i.e. comprise a sub-/set of the codewords of, an overall/comprehensive codebook. Such overall/comprehensive codebook could be as exemplified in Table 1 below.

In the overall/comprehensive codebook of Table 1 below, codebook indices 0, 1, and 4 to 11 represent an effective CSI feedback for CoMP operations/schemes JT 30 and/or CS/CB, while codebook indices 2, 3, and 12 to 15 represent an effective CSI feedback for CoMP operations/scheme DPS.

Generally, it is noted that multiple types of CQI (or feedback components) can be computed for one codebook. For example, in codebook index 4, the first stream CQI (or feedback component) is computed with muting assumption on the second

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point, hence with DPS assumption, while the CQI (or feedback component) for the second stream is an aggregated CQI (or feedback components), hence with JT and/or CS/CB assumption.

Index

Layer order

RI

gjCoMP

CoMP scheme

0

~hi "" _hi

1

Joint transmission from two points.

1

_— hi _

1

2

Joint transmission from two points, each layer from one point.

2

% ""

1

Dynamic point selection with first point as the transmitting point

3

_hi

1

Dynamic point selection with second point as the transmitting point

4

hi hi h\ _

2

Joint transmission of one layer while the other layer is transmitted from point one only. Strongest point transmits two layers while the second point transmits one layer. The second point is assumed to be muting on first layer.

5

hi hi

Jii ~ -

2

Similar as the case above, only difference is the second point is transmitting the first layer instead of second.

6

~ hi

J n hi_

1

2

Joint transmission of one layer while the other layer is transmitted from point one only. Strongest point transmits on layer while the second point transmits two layers. The first point is assumed to be muting on second layer.

7

~ hi ~

J ii hi_

1

2

Similar case as above, but the layers of the second point are re-ordered.

8

hi A2

J21 122

2

Joint transmission from two points.

9

hi A2

J22 hi

2

Joint transmission from two points, layers reordered.

15

10

hi hi

_hi 122 _

1

2

Joint transmission from two points, fallback to stronger stream from {/u,/12}

11

hi A2

J22 hi _

1

2

Joint transmission from two points, layers reordered and fallback to stronger stream from {/u ,/12} (based on reported fallback CQI)

12

hi hi

2

Dynamic point selection with first point as the transmitting point

13

J11 hi

2

Dynamic point selection with second point as the transmitting point

14

h 1 hi

1

2

Dynamic point selection with first point as the transmitting point and fallback to stronger stream from {/u, ll2}

15

_hi hi_

1

2

Dynamic point selection with second point as the transmitting point and fallback to stronger stream from {/21, l22}

Table 1: Joint coding codebook

Irrespective of the exemplary overall/comprehensive codebook of Table 1 5 and/or any one of the exemplary codebooks exemplified below, it is to be noted that (at least a simple form of) coordinated beamforming (CB) may be also performed by the CoMP controller entity using joint transmission feedback including per-point PMIs. That is, per-point PMIs in the joint CSI feedback component may represent an effective CSI feedback for CoMP operations/scheme CB (at least in a simple form). 10 As a first non-limiting example, a joint encoding or combination of RI with

RICoMP is given. In this case, the transmission hypothesis (i.e. CSS) made by the CoMP user entity is predetermined per rank. For this case, a codebook may comprise codeword indices 0, 1 and 8 of the overall/comprehensive codebook of Table 1. Such codebook for this example, comprising 3 codewords, could assume a 2-bit indication 15 (i.e. codewords having 2 bits).

As a second non-limiting example, a joint encoding or combination of RI with CSS is given. For this case, a codebook may comprise codeword indices 0, 2, 3, 8, 12 and 13 of the overall/comprehensive codebook of Table 1. Such codebook for this example, comprising 6 codewords, could assume a 3-bit indication (i.e. codewords 20 having 3 bits).

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As a third non-limiting example, a joint encoding or combination of RI with RICoMP and CSS (i.e. the transmission scheme hypothesis) is given. For this case, a codebook may comprise codeword indices 0 to 3, 8, 10, and 12 to 15 of the overall/comprehensive codebook of Table 1. Such codebook for this example, 5 comprising 10 codewords, could assume a 4-bit indication (i.e. codewords having 4 bits).

As a fourth non-limiting example, a joint encoding or combination of RI with RICoMP is given. For this case, a codebook may comprise codeword indices 0, 4, 5, 8 and 9 of the overall/comprehensive codebook of Table 1. Such codebook for this 10 example, comprising 5 codewords, could assume a 3-bit indication (i.e. codewords having 3 bits).

As a fifth non-limiting example, a joint encoding or combination of RI with CSS and ROI is given. For this case, a codebook may comprise codeword indices 0, 2, 3, 4, 5, 8, 9, 12, 13 of the overall/comprehensive codebook of Table 1. Such 15 codebook for this example, comprising 9 codewords, could assume a 4-bit indication (i.e. codewords having 4 bits).

As a sixth non-limiting example, a joint encoding or combination of RI with RICoMP and ROI is given. For this case, a codebook may comprise codeword indices 0, 1, and 4 to 11 of the overall/comprehensive codebook of Table 1. Such codebook for 20 this example, comprising 10 codewords, could assume a 4-bit indication (i.e. codewords having 4 bits).

As a seventh non-limiting example, a joint encoding or combination of RI with RICoMP, CSS and ROI is given. For this case, a codebook may comprise all of the codeword indices 0 to 15 of the overall/comprehensive codebook of Table 1. Such 25 codebook for this example, comprising 16 codewords, could assume a 4-bit indication (i.e. codewords having 4 bits).

Figure 2 shows a flowchart of an example of a procedure at a CoMP user entity according to exemplary embodiments of the present invention.

As shown in Figure 2, a corresponding procedure according to exemplary 30 embodiments of the present invention, at the CoMP user entity, comprises an operation of performing channel measurement with respect to the multiple CoMP TX points (involved in a CoMP operation/system) possibly including e.g. a serving CoMP TX transmission point, an operation of calculating per-point feedback components, including RI, PMI and CQI, based on the channel measurement with respect to a

17

single (e.g. the serving) CoMP TX point, and an operation of deducing (or evaluating) the inter-point feedback components based on the channel measurement with respect to the multiple CoMP TX points.

According to exemplary embodiments of the present invention, the channel 5 measurement with respect to the multiple CoMP TX points may be performed on the basis of a plurality of CSI-RS configurations, each of the plurality of CSI-RS configurations corresponding to transmission from one of the multiple CoMP TX points. Accordingly, the thus calculated per-point feedback components may correspond to per-CSI-RS resource feedback components (i.e. per-point feedback 10 components of a channel state information reference symbol resource per transmission point), and the inter-point feedback components may correspond to inter-CSI-RS resource feedback components (i.e. inter-point feedback components of a channel state information reference symbol resource over multiple transmission points).

15 As indicated above, the terms per/inter-point feedback components used herein may be equivalent to per/inter-CSI-RS resource feedback components when being based on channel measurement on the basis of CSI RS configurations. Accordingly, feedback per point may be regarded as feedback per configured CSI-RS resource. Yet, it is to be noted that, in case multiple points are configured under one CSI-RS 20 resource, an even more transparent feedback could be enabled, even though some of the inter-point feedback might still be needed, for example the RICoMP. Namely, the corresponding terms used herein are not to be construed to exclude such as case of multiple points being configured under one CSI-RS resource, which is also applicable according to exemplary embodiments of the present invention.

25 In this regard, the multiple CoMP TX points are included in a CoMP

measurement set for channel measurement at the CoMP user entity, for which the CoMP user entity reports results of channel measurement of those CSI-RS resources corresponding to CoMP TX points included in a CoMP cooperation/reporting set to the CoMP controller entity.

30 Generally, a CoMP measurement set is formed by M cells/points for which the

CoMP user entity is measuring channel state information. The cooperation/reporting set is limited to N cells/points defining the number of points involved in an actual CoMP scheme for which CSI feedback is reported. The common assumption is that the CoMP reporting set is formed by two to three points, while the number of points

18

actually involved in the CoMP scheme is left for network implementation. The point from which the CoMP user entity would receive transmission in single-point mode is defined as the serving CoMP TX point. Hence, the CoMP user entity will be measuring M cells/points, or more generally M CSI-RS resources. From this channel 5 measurement, the CoMP user entity reports CSI feedback for N CSI-RS resources, where it is likely that N<M holds.

For channel measurement, the CoMP user entity may be configured with multiple CSI-RS configurations, which may be received from the CoMP controller entity or any other network entity. Typically, a serving base station or access node 10 configures the CoMP user entity to measure multiple CSI-RS configurations such that one CSI-RS configuration corresponds to transmission from one CoMP TX point, i.e. the reference signals transmitted within the resources given by one CSI-RS configuration are all transmitted from the same geographical location (point). Hence, the CSI feedback measured from one CSI-RS resource typically corresponds to CSI 15 feedback for one CoMP TX point. In this regard, (e.g. PDSCH) resource element muting is also specified by way of a zero-power CSI-RS configuration, which allows for multi-cell channel estimation/evaluation due to reducing interference in channel measurement.

Namely, a CoMP user entity may measure the channel corresponding to 20 multiple CoMP TX points based on configured CSI-RS resources.

Accordingly, exemplary embodiments of the present invention may commonly utilize feedback according to different specifications in a combined manner. On the one hand, per-point feedback according to LTE Releases 8 to 10 is utilized, wherein the feedback mechanism operates per point and the CoMP user entity provides 25 RI/PMI/CQI feedback for one point. On the one hand, inter-point feedback (as under consideration for LTE Release 11) is utilized, wherein the feedback mechanism operates over multiple points and the CoMP user entity provides inter-point feedback over multiple points. This is accomplished in that the CoMP user entity may receive CSI-RS resources for more than one point and it is possible to design aggregated 30 (over multiple CSI-RS resource) or per point (per CSI-RS resource) feedback. The per-point PMIs may be improved by a combiner (inter-CSI-RS resource) feedback that may be an inter-point phase, an inter-point amplitude value and/or a point selection indicator.

19

As shown in Figure 2, a deducing operation according to exemplary embodiments of the present invention, at the CoMP user entity, may exemplarily comprise the following approach.

Namely, according to exemplary embodiments of the present invention, the 5 inter-point feedback components may be deduced (or evaluated) by an operation of calculating values of a certain channel quality information/metric (e.g. CQIs) with respect to each one of different transmission hypotheses for transmission from the multiple CoMP TX points in terms of the inter-point feedback components (e.g. one or more of RICoMP, CSS and ROI), an operation of selecting the transmission 10 hypothesis among the different transmission hypotheses, which has the highest calculated value of the certain channel quality information/metric (e.g. the highest CQI value), and an operation of utilizing the inter-point feedback components of the selected transmission hypothesis (e.g. one or more of RICoMP, CSS and ROI) as the deduced inter-point feedback components. In this regard, different hypotheses about 15 the transmission in terms of CoMP scheme (CSS) and/or CoMP rank (RICoMP) and/or layer ordering (ROI) are made, the corresponding values of a certain channel quality information/metric (e.g. CQIs) are calculated, and the transmission hypothesis is selected for inter-CSI-RS resource feedback as the one with the highest resulting channel quality information/metric (e.g. CQI). It is noted that a hysteresis may be 20 applied in this regard, namely in the selection decision.

In deducing the inter-point feedback components, as outlined above, per-point PMIs may be utilized. In this regard, PMIs with respect to each one of multiple CoMP TX points (i.e. per point PMIs) may be calculated, and the thus calculated (per-point) PMIs may be used for the channel quality information/metric based (e.g. the CQI-25 based) comparison with respect to each one of different transmission hypotheses. Specifically, the thus calculated (per-point) PMIs may be utilized (as a condition) for calculating the channel quality information/metric values (e.g. the CQIs).

Generally, a CoMP user entity may evaluate inter-CSI-RS resource feedback in terms of CoMP scheme (CSS) and/or CoMP rank (RICoMP) and/or layer ordering 30 (ROI) in different ways.

Figure 3 shows a diagram of an example of another procedure in a CoMP system according to exemplary embodiments of the present invention.

As shown in Figure 3, a corresponding procedure according to exemplary embodiments of the present invention, at the CoMP user entity, comprises an

20

operation of including the generated joint CSI feedback component into (a signaling field of) a predetermined signaling format and an operation of (periodically) transmitting the signaling format on a physical uplink control channel (PUCCH) or a physical uplink shared channel (PUSCH) to the CoMP controller entity. It may 5 optionally further comprise an operation of including PMI and CQI with respect to the serving CoMP TX point into (a signaling field of) a predetermined signaling format and an operation of (periodically) transmitting the signaling format on a physical uplink control channel (PUCCH) or a physical uplink shared channel (PUSCH) to the CoMP controller entity. A corresponding procedure according to exemplary 10 embodiments of the present invention, at the CoMP controller entity, comprises an operation of (periodically) receiving the signaling format/formats on the physical uplink control channel (PUCCH) or the physical uplink shared channel (PUSCH) from the CoMP user entity, wherein the thus received CSI feedback information is applied in the control of CoMP operations at the CoMP controller entity. 15 According to exemplary embodiments of the present invention, the aforementioned signaling formats may be the same, in which case the various feedback components are included in different signaling fields thereof, or the aforementioned signaling formats may be different signaling formats, such as e.g. different PUCCH/PUSCH reports.

20 In terms of the receiving and/or controlling/applying operation, the CoMP

controller entity may decode the CSI feedback, in particular the joint CSI feedback component, and/or the PMI and the CQI. Upon decoding, one or more of the thus decoded RI, PMI and CQI may be applied as a per-point feedback component in terms of the CoMP operation/s and/or the thus decoded at least one inter-point feedback 25 component may be applied as an inter-point feedback component in terms of the CoMP operation/s.

According to exemplary embodiments of the present invention, the CSI feedback information may thus be signaled by way of a periodic uplink reporting on the PUCCH, i.e. one or more PUCCH reports, or on the PUSCH, i.e. one or more 30 PUSCH reports.

According to exemplary embodiments of the present invention, the signaling format/s used for such uplink reporting may be any conceivable signaling format being operable on the PUCCH and/or the PUSCH. For example, in the case of

21

PUCCH reporting, specified PUCCH formats 2/2a/2b are applicable, while also other PUCCH formats may be used.

According to exemplary embodiments of the present invention, when the aforementioned optional operation is applied, the PMI and the CQI of the fallback 5 point (i.e. the serving CoMP TX point or the CoMP controller entity) are transmitted in the same PUCCH report as the CSI feedback information or a different PUCCH report than the CSI feedback information. Thereby, in connection with the jointly encoded RI, fallback support to single-point operations, i.e. conventional single-point schemes/operations, is provided. Accordingly, the CoMP TX point or the CoMP 10 controller entity serving as the fallback point is enabled to fall back to such single-point operations, as needed or appropriate, e.g. in view of the contents of the CSI feedback information or other environmental conditions or the like.

Although not depicted in Figure 3, according to exemplary embodiments of the present invention, the illustrated PUCCH report may be followed by at least one 15 PUSCH report (e.g. including CoMP hypothesis based CQI and PMI reports).

Figure 4 shows a diagram of an example of still another procedure in a CoMP system according to exemplary embodiments of the present invention.

As shown in Figure 4, in a corresponding procedure according to exemplary embodiments of the present invention, the CoMP controller entity verifies a need for 20 additional CSI feedback on the basis of at least one of the CoMP operations intended to be performed or being performed or having been performed. Namely, as a prediction for at least one CoMP operation in view of the received CSI feedback, as a result of execution of at least one CoMP operation, or as an intermediate result during execution of at least one CoMP operation, the CoMP controller entity may determine 25 that additional CSI feedback is needed or desired. Then, the CoMP controller entity transmits a request for the needed additional CSI feedback to the CoMP user entity. Upon receipt of such request from the CoMP controller entity, the CoMP user entity generates the requested additional CSI feedback, and transmits the generated additional CSI feedback to the requesting CoMP controller entity. Upon receipt of the 30 requested additional CSI feedback from the CoMP user entity, the CoMP controller entity performs at least one of the CoMP operations on the basis of the received additional CSI feedback.

According to exemplary embodiments of the present invention, as indicated in Figure 4 by way of a dashed block and usage of parentheses, the requested additional

22

CSI feedback may be transmitted from the CoMP user entity to the CoMP controller entity in a predetermined signaling format. To this end, the CoMP user entity includes the generated additional CSI feedback into (a signaling field of) a predetermined signaling format, and transmits the signaling format on a physical uplink control 5 channel (PUCCH) and/or a physical uplink shared channel (PUSCH).

According to exemplary embodiments of the present invention, the CSI feedback transmitted (in a periodic manner) on the PUCCH and/or the PUSCH provides the receiving CoMP controller entity with (preliminary) information prior to sending fully blown CoMP feedback (in an aperiodic manner) on the PUCCH and/or 10 the PUSCH. In this way, the CoMP controller entity may further estimate how the additional PUCCH/PUSCH feedback is multiplexed from different CoMP users. Namely, the additional CSI feedback information may be signaled by way of an aperiodic uplink reporting on the PUCCH and/or the PUSCH, i.e. a PUCCH/PUSCH report.

15 Thereby, exemplary embodiments of the present invention may utilize existing signaling formats, i.e. options for uplink CSI feedback reporting. On the one hand, periodic reporting on the PUCCH or the PUSCH may be utilized, in which case the CoMP user entity is configured with periodic reporting instants and is hence continuously reporting CSI feedback. On the other hand, aperiodic reporting on the 20 PUSCH may be utilized, in which case a CoMP controller entity may at any time trigger a CoMP user entity to report CSI feedback using a separate CQI trigger included in the uplink scheduling grant. Typically, the PUCCH reporting is a low rate wideband feedback, e.g. in LTE Releases 8 to 10 the maximum number of feedback payload bits is 11, while more rich (e.g. frequency selective) and hence higher rate 25 CSI feedback can be included on the PUSCH with even hundreds of payload bits.

In view of the procedures of Figures 3 and 4 above, according to exemplary embodiments of the present invention, a CoMP controller entity, upon receipt of CSI feedback (e.g. by way of a periodic PUCCH report), may perform scheduling and transmission based on the CSI feedback (in the PUCCH report), i.e. use the 30 transmission scheme and/or rank and/or layer ordering information in the context of CoMP, and/or may request from the CoMP user entity further CoMP feedback which may be transmitted over PUCCH and/or PUSCH.

23

Figure 5 shows a table illustrating a mapping of CSI feedback components in a predetermined signaling format according to conventional specifications and exemplary embodiments of the present invention.

In LTE Release 8 the CSI feedback consists of the three distinct feedback 5 components RI, PMI and CQI, wherein the CQI and the PMI feedbacks are jointly encoded while the RI feedback is encoded separately. This is due to the fact that the value of RI determines the payload of the rest of the CSI, and thus inevitable.

In LTE Release 10, the CSI feedback consists of the same quantities as in LTE Release 8 (that is CQI, RI) while for eight transmit antennas the PMI is constructed 10 from two precoding indexes PMI1 and PMI2. The PMI1 and PMI2 correspond to different precoding codebooks.

According to exemplary embodiments of the present invention, as described above, the CSI feedback consists of a jointly encoded CSI feedback (according to various options) in one signaling field or report and, at least optionally, the CQI and 15 the PMI feedbacks being jointly encoded in another signaling field or report.

As evident from Figure 5, exemplary embodiments of the present invention are capable of utilizing the same signaling format as conventional specifications, but use a different CSI feedback, namely a different mapping CSI feedback components and signaling fields or reports of the predetermined signaling format.

20 In view of the above, specific features and/or effects according to exemplary embodiments of the present invention may be summarized as follows this summary is noted to be non-exhaustive but merely illustrative/exemplary).

Exemplary embodiments of the present invention provide for a common feedback framework for coordinated multi-point operations of various coordinated 25 multi-point schemes and/or scenarios (in/for cellular communication systems). That is, there is provided a common feedback signaling design for various coordinated multi-point schemes and/or scenarios, which is effective in terms of allowing seamless coordinated multi-point operations and providing fallback support to single-point operations.

30 The common feedback framework according to exemplary embodiments of the present invention is suitable for any CoMP scenario, specifically but not exclusively aforementioned CoMP scenarios 1 to 4, which supports any CoMP scheme/category, specifically but not exclusively aforementioned CoMP

24

schemes/categories such as CoMP JT, DPS and CS/CB (with or without dynamic point blanking/muting, respectively).

The common feedback framework according to exemplary embodiments of the present invention is capable of reusing specified (LTE PUCCH and/or PUSCH) 5 signaling to a large extent.

Accordingly, by virtue of the common feedback framework according to exemplary embodiments of the present invention, implementation synergy with existing communication systems and/or network deployments (e.g. LTE releases/specifications) may be maximized. That is, the common feedback framework 10 according to exemplary embodiments of the present invention supports flexible, reliable and efficient DL CoMP without the need for (major) redesign of UL control signaling structures.

Generally, the above-described procedures and functions may be implemented by respective functional elements, processors, or the like, as described below. 15 While in the foregoing exemplary embodiments of the present invention are described mainly with reference to methods, procedures and functions, corresponding exemplary embodiments of the present invention also cover respective apparatuses, network nodes and systems, including both software, algorithms, and/or hardware thereof.

20 Respective exemplary embodiments of the present invention are described below referring to Figure 6, while for the sake of brevity reference is made to the detailed description with regard to Figures 1 to 5.

In Figure 6 below, which is noted to represent a simplified block diagram, the solid line blocks are basically configured to perform respective operations as 25 described above. The entirety of solid line blocks are basically configured to perform the methods and operations as described above, respectively. With respect to Figure 6, it is to be noted that the individual blocks are meant to illustrate respective functional blocks implementing a respective function, process or procedure, respectively. Such functional blocks are implementation-independent, i.e. may be implemented by means 30 of any kind of hardware or software, respectively. The arrows and lines interconnecting individual blocks are meant to illustrate an operational coupling therebetween, which may be a physical and/or logical coupling, which on the one hand is implementation-independent (e.g. wired or wireless) and on the other hand may also comprise an arbitrary number of intermediary functional entities not shown. The

25

direction of arrow is meant to illustrate the direction in which certain operations are performed and/or the direction in which certain data is transferred.

Further, in Figure 6, only those functional blocks are illustrated, which relate to any one of the above-described methods, procedures and functions. A skilled 5 person will acknowledge the presence of any other conventional functional blocks required for an operation of respective structural arrangements, such as e.g. a power supply, a central processing unit, respective memories or the like. Among others, memories are provided for storing programs or program instructions for controlling the individual functional entities to operate as described herein.

10 Figure 6 shows a schematic block diagram illustrating exemplary apparatuses according to exemplary embodiments of the present invention.

In view of the above, the thus illustrated apparatuses 10 and 20 are suitable for use in practicing the exemplary embodiments of the present invention, as described herein.

15 The thus illustrated apparatus 10 may represent a (part of a) CoMP user entity,

and the thus illustrated apparatus 20 may represent a (part of a) CoMP controller entity.

As described above, the CoMP user entity of apparatus 10, i.e. apparatus 10 as such, may be a (part of) a terminal side entity of a cellular communication system, 20 such as a UE or a modem (which may be installed as part of the UE, but may be also a separate module, which can be attached to various devices) or the like of a LTE/LTE-A system, and the CoMP controller entity of apparatus 20, i.e. apparatus 20 as such, may be a (part of) a network side entity of a cellular communication system, such as an eNB or a modem (which may be installed as part of the eNB, but may be also a 25 separate module, which can be attached to various devices) of a LTE/LTE-A system or the like. It is noted that the CoMP controller entity of apparatus 20, i.e. apparatus 20 as such, may be operable or implemented at/in/by different (types of) network side entities in accordance with an underlying CoMP scenario.

As indicated in Figure 6, according to exemplary embodiments of the present 30 invention, each of the apparatuses comprises a processor 11/22, a memory 12/22 and an interface 13/23, which are connected by a bus 14/24 or the like, and the apparatuses may be connected via a link 30. The link 30 may be a physical and/or logical coupling, which on the one hand is implementation-independent (e.g. wired or

26

wireless) and on the other hand may also comprise an arbitrary number of intermediary functional entities not shown in Figure 6.

The processor 11/21 and/or the interface 13/23 may be facilitated for communication over a (hardwire or wireless) link, respectively. The interface 13/23 5 may comprise a suitable receiver or a suitable transmitter-receiver combination or transceiver, which is coupled to one or more antennas or communication means for (hardwire or wireless) communications with the linked or connected device(s), respectively. The interface 13/23 is generally configured to communicate with another apparatus, i.e. the interface thereof.

10 The memory 12/22 may store respective programs assumed to include program instructions or computer program code that, when executed by the respective processor, enables the respective electronic device or apparatus to operate in accordance with the exemplary embodiments of the present invention. For example, the memory 12 of the apparatus 10 may store preconfigured CSI-RS configurations 15 for channel measurement purposes, the memory 22 of the apparatus 20 may store received CSI feedback for CoMP operation purposes, and so on.

In general terms, the respective devices/apparatuses (and/or parts thereof) may represent means for performing respective operations and/or exhibiting respective functionalities, and/or the respective devices (and/or parts thereof) may have functions 20 for performing respective operations and/or exhibiting respective functionalities.

When in the subsequent description it is stated that the processor (or some other means) is configured to perform some function, this is to be construed to be equivalent to a description stating that at least one processor, potentially in cooperation with computer program code stored in the memory of the respective 25 apparatus, is configured to cause the apparatus to perform at least the thus mentioned function. Also, such function is to be construed to be equivalently implementable by specifically configured means for performing the respective function (i.e. the expression "processor configured to [cause the apparatus to] perform xxx-ing" is construed to be equivalent to an expression such as "means for xxx-ing"). 30 According to exemplary embodiments of the present invention, an apparatus representing the apparatus 10 comprises at least one processor 11, at least one memory 12 including computer program code, and at least one interface 13 configured for communication with at least another apparatus. The apparatus 10, i.e. the processor (namely, the at least one processor 11, with the at least one memory 12

27

and the computer program code), is configured to perform generating channel state information feedback for coordinated multi-point operations, said generating comprising jointly encoding rank indicator information as a per-point feedback component with respect to a single transmission point and at least one of inter-point 5 feedback components with respect to multiple transmission points into a joint channel state information feedback component, and signaling the generated channel state information feedback to a coordinated multi-point controller entity.

In its most basic form, stated in other words, the apparatus 10 may thus comprise respective means for generating (including means for encoding) channel 10 state information feedback and means for signaling generated channel state information feedback.

As outlined above, in enhanced forms, the apparatus 10 may comprise one or more of respective means for performing channel measurement, means for calculating per-point feedback components, means for deducing inter-point feedback 15 components, means for calculating channel quality indicator information and means for selecting a transmission hypothesis, means for selecting a codeword, means for including data into a predetermined signaling format and means for periodically transmitting the signaling format, means for receiving a request, means for generating requested additional channel state information feedback, means for including 20 additional channel state information feedback into a predetermined signaling format, and means for transmitting the signaling format.

According to exemplary embodiments of the present invention, an apparatus representing the apparatus 20 comprises at least one processor 21, at least one memory 22 including computer program code, and at least one interface 23 25 configured for communication with at least another apparatus. The apparatus 20, i.e. the processor (namely, the at least one processor 21, with the at least one memory 22 and the computer program code), is configured to perform receiving channel state information feedback for coordinated multi-point operations, said channel state information feedback comprising a joint channel state information feedback 30 component in which rank indicator information as a per-point feedback component with respect to a single transmission point and at least one of inter-point feedback components with respect to multiple transmission points are jointly encoded, and controlling coordinated multi-point operations on the basis of the received channel state information feedback.

28

In its most basic form, stated in other words, the apparatus 20 may thus comprise respective means for receiving (including means for decoding) channel state information feedback and means for performing coordinated multi-point operations.

As outlined above, in enhanced forms, the apparatus 20 may comprise one or 5 more of respective means for receiving a signaling format, means for verifying a need for additional channel state information, means for transmitting a request for additional channel state information feedback, and means for receiving additional channel state information feedback.

For further details of specifics regarding functionalities according to 10 exemplary embodiments of the present invention, reference is made to the foregoing description in conjunction with Figures 1 to 5.

According to exemplarily embodiments of the present invention, a system may comprise any conceivable combination of the thus depicted devices/apparatuses and other network elements, which are configured to cooperate as described above. 15 In general, it is to be noted that respective functional blocks or elements according to above-described aspects can be implemented by any known means, either in hardware and/or software, respectively, if it is only adapted to perform the described functions of the respective parts. The mentioned method steps can be realized in individual functional blocks or by individual devices, or one or more of the 20 method steps can be realized in a single functional block or by a single device.

Generally, any structural means such as a processor or other circuitry may refer to one or more of the following: (a) hardware-only circuit implementations (such as implementations in only analog and/or digital circuitry) and (b) combinations of circuits and software (and/or firmware), such as (as applicable): (i) a combination of 25 processor(s) or (ii) portions of processor(s)/software (including digital signal processor(s)), software, and memory(ies) that work together to cause an apparatus, such as a mobile phone or server, to perform various functions) and (c) circuits, such as a microprocessor(s) or a portion of a microprocessor(s), that require software or firmware for operation, even if the software or firmware is not physically present. 30 Also, it may also cover an implementation of merely a processor (or multiple processors) or portion of a processor and its (or their) accompanying software and/or firmware, any integrated circuit, or the like.

Generally, any procedural step or functionality is suitable to be implemented as software or by hardware without changing the idea of the present invention. Such

29

software may be software code independent and can be specified using any known or future developed programming language, such as e.g. Java, C++, C, and Assembler, as long as the functionality defined by the method steps is preserved. Such hardware may be hardware type independent and can be implemented using any known or 5 future developed hardware technology or any hybrids of these, such as MOS (Metal Oxide Semiconductor), CMOS (Complementary MOS), BiMOS (Bipolar MOS), BiCMOS (Bipolar CMOS), ECL (Emitter Coupled Logic), TTL (Transistor-Transistor Logic), etc., using for example ASIC (Application Specific IC (Integrated Circuit)) components, FPGA (Field-programmable Gate Arrays) components, CPLD 10 (Complex Programmable Logic Device) components or DSP (Digital Signal Processor) components. A device/apparatus may be represented by a semiconductor chip, a chipset, system in package, or a (hardware) module comprising such chip or chipset; this, however, does not exclude the possibility that a functionality of a device/apparatus or module, instead of being hardware implemented, be implemented 15 as software in a (software) module such as a computer program or a computer program product comprising executable software code portions for execution/being run on a processor. A device may be regarded as a device/apparatus or as an assembly of more than one device/apparatus, whether functionally in cooperation with each other or functionally independently of each other but in a same device housing, for 20 example.

Apparatuses and/or means or parts thereof can be implemented as individual devices, but this does not exclude that they may be implemented in a distributed fashion throughout the system, as long as the functionality of the device is preserved. Such and similar principles are to be considered as known to a skilled person. 25 Software in the sense of the present description comprises software code as such comprising code means or portions or a computer program or a computer program product for performing the respective functions, as well as software (or a computer program or a computer program product) embodied on a tangible medium such as a computer-readable (storage) medium having stored thereon a respective data 30 structure or code means/portions or embodied in a signal or in a chip, potentially during processing thereof.

The present invention also covers any conceivable combination of method steps and operations described above, and any conceivable combination of nodes,

30

apparatuses, modules or elements described above, as long as the above-described concepts of methodology and structural arrangement are applicable.

In view of the above, the present invention and/or exemplary embodiments thereof provide measures for realizing a common feedback framework for coordinated 5 multi-point operations of various coordinated multi-point schemes and/or scenarios. Such measures may exemplarily comprise generation of channel state information feedback for coordinated multi-point operations, said generating comprising jointly encoding rank indicator information as a per-point feedback component with respect to a single transmission point and at least one of inter-point feedback components 10 with respect to multiple transmission points into a joint channel state information feedback component, signaling of the generated channel state information feedback from a coordinated multi-point user entity to a coordinated multi-point controller entity, and control of coordinated multi-point operations on the basis of the received channel state information feedback at the coordinated multi-point controller entity. 15 The measures according to exemplary embodiments of the present invention may be applied for any kind of network environment, such as for example for communication systems in accordance with any one of 3GPP standards, LTE standards of release 11/12/... (including LTE-Advanced and its evolutions), UMTS standards, and WCDMA standards. In particular, the measures according to exemplary embodiments 20 of the present invention may be applied to any CoMP and/or MIMO techniques which are a feature e.g. of 3GPP LTE standards of release 11/12 and onwards.

Even though the present invention and/or exemplary embodiments are described above with reference to the examples according to the accompanying drawings, it is to be understood that they are not restricted thereto. Rather, it is 25 apparent to those skilled in the art that the present invention can be modified in many ways without departing from the scope of the inventive idea as disclosed herein.

List of acronyms and abbreviations

30 3GPP 3rd Generation Partnership Project

BS Base Station

CB Coordinated Beamforming

CoMP Coordinated Multi-Point (Transmission/Reception)

CQI Channel Quality Indicator

31

cs

Coordinated Scheduling

CSI

Channel State Information

CSI-RS

CSI Reference Symbol

DL

Downlink

DM-RS

Demodulation Reference Symbol

DPS

Dynamic Point Selection

JP

Joint Processing

JT

Joint Transmission

LTE

Long Term Evolution

LTE-A

Long Term Evolution Advanced

MIMO

Multiple-Input Multiple-Output

MU

Multi-User

PMI

Precoding Matrix Indicator

PUSCH

Physical Uplink Shared Channel

PUCCH

Physical Uplink Control Channel

RI

Rank Indicator

ROI

Rank Order Indicator

SU

Single-User

TX

Transmission

UE

User Equipment

UL

Uplink

UMTS

Universal Mobile Telecommunications System

WCDMA

Wideband Code Division Multiple Access

32

Claims

Claims

1. A communications method comprising:

generating channel state information feedback for coordinated multi-point 5 operations, said generating comprising jointly encoding rank indicator information as a per-point feedback component with respect to a single transmission point and at least one of inter-point feedback components with respect to multiple transmission points into a joint channel state information feedback component, and signaling the generated channel state information feedback to a coordinated 10 multi-point controller entity.

2. The method according to claim 1, further comprising:

performing channel measurement with respect to the multiple transmission points including the single transmission point,

15 calculating per-point feedback components, including the rank indicator information, precoding matrix indicator information and channel quality indicator information, based on the channel measurement with respect to the single transmission point, and deducing the inter-point feedback components based on the channel 20 measurement with respect to the multiple transmission points.

3. The method according to claim 2, wherein the channel measurement with respect to the multiple transmission points is performed on the basis of a plurality of channel state information reference symbol 25 configurations, each of the plurality of channel state information reference symbol configurations corresponding to transmission from one of the multiple transmission points, and/or the calculated per-point feedback components correspond to per-point feedback components of a channel state information reference symbol resource per 30 transmission point, and the inter-point feedback components correspond to inter-point feedback components of a channel state information reference symbol resource over multiple transmission points.

4. The method according to claim 2 or 3, wherein the deducing comprises

33

calculating channel quality metric with respect to each one of different transmission hypotheses for transmission from the multiple transmission points in terms of the inter-point feedback components,

selecting the transmission hypothesis among the different transmission 5 hypotheses, which has the highest value of the calculated channel quality metric, and utilizing the inter-point feedback components of the selected transmission hypothesis as the deduced inter-point feedback components.

5. The method according to any one of claims 1 to 4, wherein the inter-10 point feedback components comprise at least one of:

coordinated multi-point rank indicator information,

coordinated multi-point scheme selection information, and layer order indicator information of transmission layers between a number of transmission points corresponding to the coordinated multi-point rank indicator 15 information.

6. The method according to claim 5, wherein the jointly encoding comprises one of:

jointly encoding the rank indicator information and the coordinated multi-20 point rank indicator information into the joint channel state information feedback component,

jointly encoding the rank indicator information and the coordinated multipoint scheme selection information into the joint channel state information feedback component,

25 jointly encoding the rank indicator information and the coordinated multi point rank indicator information and the coordinated multi-point scheme selection information into the joint channel state information feedback component,

jointly encoding the rank indicator information and the layer order indicator information into the joint channel state information feedback component, 30 jointly encoding the rank indicator information and the coordinated multi point scheme selection information and the layer order indicator information into the joint channel state information feedback component,

34

jointly encoding the rank indicator information and the coordinated multipoint rank indicator information and the layer order indicator information into the joint channel state information feedback component, and jointly encoding the rank indicator information and the coordinated multi-5 point rank indicator information and the coordinated multi-point scheme selection information and the layer order indicator information into the joint channel state information feedback component.

7. The method according to any one of claims 1 to 6, wherein the 10 generating comprises:

selecting a codeword for the channel state information feedback in accordance with the at least one inter-point feedback component being jointly encoded with the rank indicator information into the joint channel state information feedback component.

15

8. The method according to any one of claims 1 to 7, wherein the signaling comprises including the generated joint channel state information feedback component into a predetermined signaling format, and 20 periodically transmitting the signaling format on a physical uplink control channel or a physical uplink shared channel to the coordinated multi-point controller entity.

9. The method according to claim 8, further comprising:

25 including precoding matrix indicator information and channel quality indicator information with respect to the single transmission point into a predetermined signaling format, and periodically transmitting the signaling format on a physical uplink control channel or a physical uplink shared channel to the coordinated multi-point controller 30 entity.

10. The method according to any one of claims 1 to 9, further comprising receiving a request for additional channel state information feedback from the coordinated multi-point controller entity,

35

generating the requested additional channel state information feedback, including the generated additional channel state information feedback into a predetermined signaling format, and transmitting the signaling format on a physical uplink shared channel to the 5 coordinated multi-point controller entity.

11. A communications method comprising:

receiving channel state information feedback for coordinated multi-point operations, said channel state information feedback comprising a joint channel state 10 information feedback component in which rank indicator information as a per-point feedback component with respect to a single transmission point and at least one of inter-point feedback components with respect to multiple transmission points are jointly encoded, and controlling coordinated multi-point operations on the basis of the received 15 channel state information feedback.

12. The method according to claim 11, wherein the coordinated multi-point operations comprise at least one of:

a joint transmission coordinated multi-point scheme,

20 a dynamic point selection coordinated multi-point scheme, and a coordinated scheduling and/or beamforming coordinated multi-point scheme.

13. The method according to claim 11 or 12, wherein the at least one of inter-point feedback components comprises inter-point feedback components of a

25 selected transmission hypothesis from the multiple transmission points.

14. The method according to any one of claims 11 to 13, wherein the per-point feedback component corresponds to a per-point feedback component of a channel state information reference symbol resource per transmission 30 point, and the inter-point feedback components correspond to inter-point feedback components of a channel state information reference symbol resource over multiple transmission points.

36

15. The method according to any one of claims 11 to 14, wherein the inter-point feedback components comprise:

coordinated multi-point rank indicator information,

coordinated multi-point scheme selection information, and 5 layer order indicator information of transmission layers between a number of transmission points corresponding to the coordinated multi-point rank indicator information.

16. The method according to claim 15, wherein in the joint channel state 10 information feedback component the rank indicator information is jointly encoded with one of:

the coordinated multi-point rank indicator information,

the coordinated multi-point scheme selection information,

the coordinated multi-point rank indicator information and the coordinated 15 multi-point scheme selection information,

the layer order indicator information,

the coordinated multi-point scheme selection information and the layer order indicator information,

the coordinated multi-point rank indicator information and the layer order 20 indicator information, and the coordinated multi-point rank indicator information and the coordinated multi-point scheme selection information and the layer order indicator information.

17. The method according to any one of claims 11 to 16, wherein the 25 channel state information feedback corresponds to a codeword in accordance with the at least one inter-point feedback component being jointly encoded with the rank indicator information into the joint channel state information feedback component.

18. The method according to any one of claims 11 to 17, wherein the 30 receiving comprises periodically receiving a signaling format on a physical uplink control channel or a physical uplink shared channel, wherein the joint channel state information feedback component is included in the predetermined signaling format.

37

19. The method according to claim 18, wherein the receiving comprises periodically receiving a signaling format on a physical uplink control channel or a physical uplink shared channel, wherein precoding matrix indicator information and channel quality indicator information with respect to the single transmission point 5 are included in the predetermined signaling format.

20. The method according to any one of claims 11 to 19, further comprising verifying a need for additional channel state information feedback on the basis 10 of at least one of the coordinated multi-point operations intended to be performed or being performed or having been performed,

transmitting a request for needed additional channel state information feedback,

receiving the additional channel state information feedback, and 15 controlling coordinated multi-point operations on the basis of the received additional channel state information feedback.

21. The method according to claim 20, wherein the additional channel state information feedback are received in a predetermined signaling format on a physical

20 uplink control channel and/or a physical uplink shared channel.

22. An apparatus for use on a terminal side of a wireless communications system, the apparatus comprising:

a processing system arranged to cause the apparatus to perform: 25 generating channel state information feedback for coordinated multi-point operations, said generating comprising jointly encoding rank indicator information as a per-point feedback component with respect to a single transmission point and at least one of inter-point feedback components with respect to multiple transmission points into a joint channel state information feedback component, and 30 signaling the generated channel state information feedback to a coordinated multi-point controller entity.

23. The apparatus according to claim 22, wherein the processing system is arranged to cause the apparatus to perform:

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performing channel measurement with respect to the multiple transmission points including the single transmission point,

calculating per-point feedback components, including the rank indicator information, precoding matrix indicator information and channel quality indicator 5 information, based on the channel measurement with respect to the single transmission point, and deducing the inter-point feedback components based on the channel measurement with respect to the multiple transmission points.

10 24. The apparatus according to claim 23, wherein the channel measurement with respect to the multiple transmission points is arranged to be performed on the basis of a plurality of channel state information reference symbol configurations, each of the plurality of channel state information reference symbol configurations corresponding to transmission from one of the 15 multiple coordinated multi-point transmission points, and/or the calculated per-point feedback components correspond to per-point feedback components of a channel state information reference symbol resource per transmission point, and the inter-point feedback components correspond to inter-point feedback components of a channel state information reference symbol resource over 20 multiple transmission points.

25. The apparatus according to claim 23 or 24, wherein the processing system is arranged to cause the apparatus to perform:

calculating channel quality metric with respect to each one of different 25 transmission hypotheses for transmission from the multiple transmission points in terms of the inter-point feedback components,

selecting the transmission hypothesis among the different transmission hypotheses, which has the highest value of the calculated channel quality metric, and utilizing the inter-point feedback components of the selected transmission 30 hypothesis as the inter-point feedback components.

26. The apparatus according to any one of claims 22 to 25, wherein the inter-point feedback components comprise at least one of coordinated multi-point rank indicator information,

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coordinated multi-point scheme selection information, and layer order indicator information of transmission layers between a number of coordinated multi-point transmission points corresponding to the coordinated multipoint rank indicator information.

5

27. The apparatus according to claim 26, wherein the processing system is arranged to cause the apparatus to perform:

jointly encoding the rank indicator information and the coordinated multipoint rank indicator information into the joint channel state information feedback 10 component,

jointly encoding the rank indicator information and the coordinated multipoint scheme selection information into the joint channel state information feedback component,

jointly encoding the rank indicator information and the coordinated multi-15 point rank indicator information and the coordinated multi-point scheme selection information into the joint channel state information feedback component,

jointly encoding the rank indicator information and the rank layer indicator information into the joint channel state information feedback component,

jointly encoding the rank indicator information and the coordinated multi-20 point scheme selection information and the layer order indicator information into the joint channel state information feedback component,

jointly encoding the rank indicator information and the coordinated multipoint rank indicator information and the layer order indicator information into the joint channel state information feedback component, and 25 jointly encoding the rank indicator information and the coordinated multi point rank indicator information and the coordinated multi-point scheme selection information and the layer order indicator information into the joint channel state information feedback component.

30 28. The apparatus according to any one of claims 22 to 27, wherein the processing system is arranged to cause the apparatus to perform:

selecting a codeword for the channel state information feedback in accordance with the at least one inter-point feedback component being jointly encoded with the

40

rank indicator information into the joint channel state information feedback component.

29. The apparatus according to any one of claims 22 to 28, wherein the 5 processing system is arranged to cause the apparatus to perform:

including the generated joint channel state information feedback component into a predetermined signaling format, and periodically transmitting the signaling format on a physical uplink control channel or a physical uplink shared channel to the coordinated multi-point controller 10 entity.

30. The apparatus according to claim 29, wherein the processing system is arranged to cause the apparatus to perform:

including precoding matrix indicator information and channel quality indicator 15 information with respect to the single transmission point into a predetermined signaling format, and periodically transmitting the signaling format on a physical uplink control channel or a physical uplink shared channel to the coordinated multi-point controller entity.

20

31. The apparatus according to any one of claims 22 to 30, wherein the processing system is arranged to cause the apparatus to perform:

receiving a request for additional channel state information feedback from the coordinated multi-point controller entity,

25 generating the requested additional channel state information feedback,

including the generated additional channel state information feedback into a predetermined signaling format, and transmitting the signaling format on a physical uplink shared channel to the coordinated multi-point controller entity.

30

32. The apparatus according to any one of claims 22 to 31, wherein the apparatus is operable as or at a terminal, user equipment, mobile station or modem, and/or the apparatus is operable in at least one of a LTE and a LTE-A cellular system.

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33. An apparatus for use on a network side of a wireless communications system, the apparatus comprising:

a processing system arranged to cause the apparatus to perform: 5 receiving channel state information feedback for coordinated multi-point operations, said channel state information feedback comprising a joint channel state information feedback component in which rank indicator information as a per-point feedback component with respect to a single transmission point and at least one of inter-point feedback components with respect to multiple transmission points are 10 jointly encoded, and controlling coordinated multi-point operations on the basis of the received channel state information feedback.

34. The apparatus according to claim 33, wherein the coordinated multi-15 point operations comprise at least one of:

a joint transmission coordinated multi-point scheme,

a dynamic point selection coordinated multi-point scheme, and a coordinated scheduling and/or beamforming coordinated multi-point scheme.

20 35. The apparatus according to claim 33 or 34, wherein the at least one of inter-point feedback components comprises:

inter-point feedback components of a selected transmission hypothesis from the multiple transmission points.

25 36. The apparatus according to any one of claims 33 to 35, wherein the per-point feedback component corresponds to a per-point feedback component of a channel state information reference symbol resource per transmission point, and the inter-point feedback components correspond to inter-point feedback components of a channel state information reference symbol resource over multiple 30 transmission points.

37. The apparatus according to any one of claims 33 to 36, wherein the inter-point feedback components comprise coordinated multi-point rank indicator information,

42

coordinated multi-point scheme selection information, and layer order indicator information of transmission layers between a number of transmission points corresponding to the coordinated multi-point rank indicator information.

5

38. The apparatus according to claim 37, wherein in the joint channel state information feedback component the rank indicator information is jointly encoded with one of:

the coordinated multi-point rank indicator information, 10 the coordinated multi-point scheme selection information,

the coordinated multi-point rank indicator information and the coordinated multi-point scheme selection information,

the layer order indicator information,

the coordinated multi-point scheme selection information and the layer order 15 indicator information,

the coordinated multi-point rank indicator information and the layer order indicator information, and the coordinated multi-point rank indicator information and the coordinated multi-point scheme selection information and the layer order indicator information.

20

39. The apparatus according to any one of claims 33 to 38, wherein the channel state information feedback corresponds to a codeword in accordance with the at least one inter-point feedback component being jointly encoded with the rank indicator information into the joint channel state information feedback component.

25

40. The apparatus according to any one of claims 33 to 39, wherein the processing system is arranged to cause the apparatus to perform:

periodically receiving a signaling format on a physical uplink control channel or a physical uplink shared channel, wherein the joint channel state information 30 feedback component is included in the predetermined signaling format.

41. The apparatus according to claim 40, wherein the processing system is arranged to cause the apparatus to perform:

43

periodically receiving a signaling format on a physical uplink control channel or a physical uplink shared channel, wherein precoding matrix indicator information and channel quality indicator information with respect to the single transmission point are included in the predetermined signaling format.

5

42. The apparatus according to any one of claims 33 to 41, wherein the processing system is arranged to cause the apparatus to perform:

verifying a need for additional channel state information feedback on the basis of at least one of the coordinated multi-point operations intended to be performed or

10 being performed or having been performed,

transmitting a request for needed additional channel state information feedback,

receiving the additional channel state information feedback, and controlling coordinated multi-point operations on the basis of the received

15 additional channel state information feedback.

43. The apparatus according to claim 42, wherein the additional channel state information feedback are received in a predetermined signaling format on a physical uplink control channel and/or a physical uplink shared channel.

20

44. The apparatus according to any one of claims 33 to 43, wherein the apparatus is operable as or at a base station, access point, network entity or modem, and/or the apparatus is operable in at least one of a LTE and a LTE-A cellular system.

25

45. A computer program product comprising a set of instructions which, when executed on an apparatus, is configured to cause the apparatus to carry out the method according to any one of claims 1 to 10.

30 46. A computer program product comprising a set of instructions which,

when executed on an apparatus, is configured to cause the apparatus to carry out the method according to any one of claims 11 to 21.

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47. The computer program product according to claim 45 or 46, embodied a computer-readable medium.